From now on, if I say "I could care less" about something, it means I care more than you think I do but less than you want me to.
So if I say I could care less about your collection of model trains, it means I do care, because you're my friend and I care about all the things you do, but I don't think it's nearly as important or amazing as you clearly want me to because seriously, they're just really expensive toys for grown-ups.
I could care less about my cousin's third wedding. She obviously thinks it's important enough to invite me to, and I wish nothing but the best for her and her third wife, but I just can't justify the expense of going.
I could care less about my boss's new baby. I genuinely do appreciate him being out of the office for the next six weeks, but it's just not that important.
I could care less if you try to "correct" my use of this phrase. Your smug "correction" will bother me briefly, but then I will link you to this post and be done with the matter. And if you're an arsehole who declares I'm wrong anyway? I couldn't care less.